1. Field of the Invention
The present general inventive concept relates to a multi-pass type color image forming apparatus, and more particularly, to a multi-pass type color image forming apparatus which is provided with one photosensitive drum and one exposure unit, forms a color toner image on an intermediate transfer member by repeating exposure, development and transfer with respect to respective colors, and transfers and fixes the color toner image on a recording medium, such as, a paper.
2. Description of the Related Art
Generally, a color image forming apparatus using an electrophotographic process is configured such that a light beam is scanned to a photosensitive member charged with a certain electric potential to form an electrostatic latent image thereon. The electrostatic latent image is developed to a toner image by using a certain color toner, and the toner image is transferred and fixed to a paper to form a color image.
Color of the toner used in the color image forming apparatus generally includes yellow (Y), magenta (M), cyan (C) and black (K). Accordingly, in order to adhere the four-color toner to the electrostatic latent image, four developing devices are needed.
A color image forming process is classified into a single pass process which is equipped with four exposure units and four photosensitive members, and a multi-pass process which is equipped with a single exposure unit and a single photosensitive member.
A multi-pass type color image forming apparatus includes one photosensitive drum and one exposure unit, and is configured such that exposure, development and transfer are repeated with respect to respective colors to form a color toner image on an intermediate transfer member, and the color toner image is transferred and fixed to a paper.
In such a multi-pass type color image forming apparatus, four developing devices get power from a driving motor. All four developing devices are not necessarily driven at the same time, and are selectively driven according to the color image.
In such a multi-pass type color image forming apparatus, four developing devices are sequentially operated. It is preferable that only a developing roller of the selected developing device (e.g., Y) is rotated, and developing rollers of the remaining developing devices (e.g., M, C and K) are not rotated.
To this end, a conventional multi-pass type color image forming apparatus includes a power transmission device for selectively transmitting a driving force from a driving motor to four developing devices, and a cam device for operating the power transmission device so that the driving force is transmitted to the selected developing device as a cam provided at a camshaft is rotated.
However, in operating the cam device, a slip is generated between the cam device and the power transmission device so that the driving force cannot be transmitted timely to the selected developing device or the driving force is transmitted to the wrong developing device.